iOS ViewController点击空白处收起键盘

点击ViewController空白处时收起键盘，可以通过系统的touchesBegan方法实现，具体如下：

Objective-C 版

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [self.view endEditing:YES];
}

Swift 版

// 收起键盘
override func touchesBegan(touches: Set, withEvent event: UIEvent?) {
    self.view.endEditing(true)
}